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  • Chemistry  (41)
  • Glutathione peroxidase  (3)
  • Escherichia coli  (2)
  • 1
    Electronic Resource
    Electronic Resource
    The selenium state of healthy children (1977)
    Springer
    European journal of pediatrics 125 (1977), S. 81-88 
    Details
    ISSN: 1432-1076
    Keywords: Selenium ; Glutathione peroxidase ; Normal values ; Blood ; Infants ; Children ; Milk ; Nutrition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The selenium concentration of serum is age-dependent. The median value at birth ( $$\tilde x$$ =50×10−9g/ml) amounts to half of the median value of adults ( $$\tilde x$$ =102×10−9g/ml). After a decrease in early infancy to $$\tilde x$$ =34×10−9g/ml it steadily increases to $$\tilde x$$ =58×10−9g/ml in the second half of the first year, to $$\tilde x$$ =82×10−9g/ml in 1–5 year old children, and to $$\tilde x$$ =92×10−9g/ml in school children. The activities of the selenium containing enzyme glutathione peroxidase of erythrocytes are also reduced in early infancy (x=7.2±0.36 U37/g Hb), whereas the enzyme activities of cord blood erythrocytes (x=8.72±0.76 U37/g Hb) are in the same range as those of older children or adults. The selenium content of some commercially available milk formulas for infants are lower than those of human and cow's milk.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00470608
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  • 2
    Electronic Resource
    Electronic Resource
    Selenium requirements in patients with inborn errors of amino acid metabolism and selenium deficiency (1980)
    Springer
    European journal of pediatrics 134 (1980), S. 65-68 
    Details
    ISSN: 1432-1076
    Keywords: Selenium ; Glutathione peroxidase ; Selenium deficiency ; Selenium supplementation ; Nutrition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The diets of 5 patients with phenylketonuria or maple-syrup-urine disease were supplemented with yeast which was rich in selenium. For 120 days the patients received 45 μg Se/day to increase the Se content of their diets to 10–12ng Se/Kjoule. Before supplementation the selenium content of serum (5–15 ng/ml) and whole blood (10–27 ng/ml), and the activity of the erythrocyte glutathione peroxidase (0.19–2.69 U37/g Hb), amounted to only 10–20% of normal. The serum selenium content reached normal values within 4 weeks of supplementation, followed by normalisation of the selenium content of whole blood within 4–8 weeks. Restoration of the activity of erythrocyte glutathione peroxidase took 9 to 15 weeks —the red cell life span. There was a significant positive correlation between the selenium content of the erythrocytes and the activity of erythrocyte glutathione peroxidase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00442405
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  • 3
    Electronic Resource
    Electronic Resource
    Plasma glutathione peroxidase after selenium supplementation in patients with reduced selenium state (1982)
    Springer
    European journal of pediatrics 138 (1982), S. 138-140 
    Details
    ISSN: 1432-1076
    Keywords: Selenium ; Supplementation ; Plasma ; Glutathione peroxidase ; Glutathione S-transferase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The plasma glutathione peroxidase (GSHPx) activity was measured in normal adults and children and in patients with reduced selenium state because of dietary treatment of metabolic diseases (phenylketonuria or maple-syrup-urine disease) before and after selenium supplementation. Besides GSHPx (measured with t-butyl hydroperoxide, cumene hydroperoxide and hydrogen peroxide as acceptor substrates) the activity of glutathione S-transferase was estimated in plasma. Plasma GSHPx activity in healthy children was significantly lower than in healthy adults. In 11 dietetically treated patients with phenylketonuria or maple-syrup-urine disease the plasma GSHPx was reduced to about 17% of the values of healthy children of the same age. No glutathione S-transferase activity could be found in plasma of children in normal or reduced Se state. During administration of yeast rich in Se (200μg Se/d) for 90 days 2 healthy adults showed no significant change of plasma GSHPx activity. During Se supplementation (75–100μg Se/d) for 120–163 days 5 dietetically treated patients with PKU or MSUD exhibited a significant increase of plasma GSHPx activity within 2 days. The values reached a plateau after 1 to 3 weeks of supplementation and remained at this level within the following 4 to 5 months. Therefore, the activity of plasma glutathione peroxidase can be used as an indicator of short-term changes of selenium intake in selenium deficient individuals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00441140
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  • 4
    Electronic Resource
    Electronic Resource
    Studies in vivo on Escherichia coli RNA polymerase mutants altered in the stringent response (1988)
    Springer
    Molecular genetics and genomics 213 (1988), S. 379-387 
    Details
    ISSN: 1617-4623
    Keywords: Stringent control ; RNA polymerase ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Previous studies on two Escherichia coli rpoB mutants, carrying single amino acid substitutions at approximate amino acid positions 736 and 906 in the β subunit, showed that these alterations in the RNA polymerase resulted in an apparent reduced response to valine-induced amino acid starvation in vivo and prevented ppGpp-mediated inhibition of transcriptional initiation at stable RNA promoters in vitro. These observations suggested that the mutations had altered either the ppGpp binding site or the promoter selectivity of the enzyme. The in vivo analysis presented here indicates that these mutants encode an RNA polymerase that responds normally to changes in the level of ppGpp; their apparent relaxedness is due to a reduced accumulation of ppGpp during isoleucine starvation. Thus, there is no indication that the mutations have altered ppGpp binding sites. These observations and the difference between in vitro and in vivo results can be explained by the assumption that the mutations produce an extended ppGpp-dependent pausing of RNA polymerase during the transcription of unstable RNA. Comparison of the vivo and in vitro effects of ppGpp on rrn transcription further suggests that these reflect different phenomena, although in both cases ppGpp inhibits rrn transcription.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00339606
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  • 5
    Electronic Resource
    Electronic Resource
    Chromosome replication in Escherichia coli induced by oversupply of DnaA (1988)
    Springer
    Molecular genetics and genomics 211 (1988), S. 138-142 
    Details
    ISSN: 1617-4623
    Keywords: Escherichia coli ; DnaA ; Replication initiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Overexpression of DnaA protein from a multicopy plasmid accompanied by a shift to 42°C causes initiation of one extra round of replication in a dnaA + strain grown in glycerol minimal medium. This extra round of replication does not lead to an extra cell division, such that cells contain twice the normal number of chromosomes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00338404
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  • 6
    Electronic Resource
    Electronic Resource
    Herstellung und Eigenschaften von Aluminiumaquoxid. I. Böhmit aus Aluminiumnitrat und Ammoniakwasser (1989)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 579 (1989), S. 211-220 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Preparation and Properties of Aluminium Hydroxide. I. Boehmite from Aluminium Nitrate and AmmoniaThe physical-chemical properties of mainly boehmite containing aluminium hydroxide are studied which were made by continuous precipitation from aluminium nitrate solution with ammonia liquor using technical raw materials and test conditions being very similar to those applied in production. The influence of the precipitation conditions (pH value, temperature, concentration and residence time in the precipitation solution) on the composition, structure and texture of the precipitation products is investigated and information about their effect on the filtration behaviour are given.In the case of a continuous precipitation it is possible to obtain phase-pure boehmite being relatively well crystallised. The crystallinity and dispersity of the precipitated hydroxide determine their filterability and the cavity structure.
    Notes: Es werden die physikalisch-chemischen Eigenschaften von vorwiegend Böhmit enthaltenden Aluminiumaquoxiden untersucht, die durch kontinuierliches Fällen aus Aluminiumnitratlösung mit Ammoniakwasser unter Verwendung technischer Rohstoffe und bei produktionsnaher Versuchsführung hergestellt wurden. Der Einfluß der Fällbedingungen (pH-Wert, Temperatur, Konzentration und Verweilzeit in der Fällsuspension) auf die chemische Zusammensetzung, Struktur und Textur der Fällprodukte wird erforscht und über deren Auswirkung auf das Filtrationsverhalten berichtet. Im Unterschied zur diskontinuierlichen Arbeitsweise kann bei kontinuierlichem Fällen bereits nach kurzen Verweilzeiten phasenreiner, relativ gut kristalliner Böhmit erhalten werden, dessen Filtrierbarkeit mit den morphologischen Eigenschaften der Niederschläge variiert.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19895790125
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  • 7
    Electronic Resource
    Electronic Resource
    Untersuchungen an oxidischen Katalysatoren. XLVI. Synthetische Boroalumosilicate mit Pentasilstruktur (SABO): Strukturelle, oberflächenchemische und katalytische EigenschaftenProfessor Ch. M. Minačew zum 80. Geburtstage am 24. Dezember 1988 gewidmet (1988)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 566 (1988), S. 39-48 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Studies on Oxide Catalysts. XLVI. Synthetic Boroaluminosilicates with Pentasil Structure (SABO): Structural, Surface Chemical, and Catalytical PropertiesA remarkable modification of ZSM-5 type zeolites is possible by isomorphous substitution of silicon and/or aluminium by boron. In the H-forms of these SABO zeolites the boron atoms mainly exist in a trigonal lattice oxygen environment and hence they are not envolved in the formation of Broensted acid sites. Consequences of incorporated boron for catalytic reactions result from a decrease in the strength of existing Broensted sites as well as from a partial lattice contraction.
    Notes: Eine bemerkenswerte Modifizierung von Zeolithen des ZSM-5-Typs gelingt auf dem Wege der isomorphen Substitution von Silicium und/oder Aluminium durch Bor. In den H-Formen derartiger SABO-Zeolithe liegt Bor bevorzugt in trigonaler Gittersauerstoffkoordination vor und ist 30mit an der Bildung von Brönsted-Säurezentren nicht beteiligt. Konsequenzen eines isomorphen Boreinbaus für katalytische Reaktionen ergeben sich im wesentlichen aus einer Verringerung der Stärke vorhandener Brönsted-Zentren sowie aus einer mehr oder weniger starken Gitterkontraktion.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19885660106
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  • 8
    Electronic Resource
    Electronic Resource
    Untersuchungen an oxidischen Katalysatoren. XLIV. Beeinflussung des katalytischen Verhaltens modifizierter Zeolithe vom Typ ZSM-5 durch thermische BehandlungProfessor Wolfgang Wieker zum 60. Geburtstage am 19. April 1987 gewidmet (1987)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 547 (1987), S. 142-148 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Studies on Oxide Catalysts. XLIV. Modification of the Catalytic Behavior of Modified ZSM-5 Zeolites by Thermal TreatmentThe catalytic activity, the shape selectivity, and the deactivation behavior of ZSM-5 in paraffin cracking reactions can be regulated by a thermal pretreatment. A minimum of the deactivation rate as a function of zeolite pretreatment time at 600°C found in the hexane cracking could be verified in the methanol conversion reaction to gasoline.
    Notes: Die katalytische Aktivität, die Formselektivität und das Aktivität-Zeit-Verhalten des ZSM-5 beim Spalten von Paraffinen kann durch thermische Vorbehandlung stark beeinflußt werden. Ein in der Spaltung von Hexan gefundenes Minimum der Desaktivierungsgeschwindigkeit als Funktion der Dauer der Vorbehandlung bei 600°C konnte in der Methanolumwandlung zu Benzin verifiziert werden.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19875470416
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  • 9
    Electronic Resource
    Electronic Resource
    Untersuchungen an oxidischen Katalysatoren, XX. Über den Einfluß der Chromoxidkonzentration auf die Thermische Alterung von Al2O3/Cr2O3/K2O-Tränkkatalysatoren der Dehydrocyclisierung (1974)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 407 (1974), S. 51-61 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Studies on Oxide Catalysts. XX. On the Influence of the Chromia Concentration on the Thermal Aging of Al2O3/Cr2O3/K2O Dehydrocyclization Catalysts Made by ImpregnationIt is reported on the thermal aging of catalysts containing 20% Cr2O3 + 4% K2O, 10% Cr2O3 + 2% K2O, 5% Cr2O3 + 1% K2O and 2.5% Cr2O3 + 0.5% K2O. Both catalysts with a high content of chromia (and potassium oxide) are characterized by high thermal stability. The portion of irreversible aging compared with that of the reversible aging decreases with increasing chromia concentration: A “reserve” of chromia is an important prerequisite to the regenerability of the catalysts.
    Notes: Es wird über die thermische Alterung von Katalysatoren berichtet, die 20% Cr2O3 + 4% K2O, 10% Cr2O3 + 2% K2O, 5% Cr2O3 + 1% K2O bzw. 2,5% Cr2O3 + 0,5% K2O auf γ-Al2O3 als Träger enthalten. Die beiden Katalysatoren hoher Chromoxid- (und Kaliumoxid-) Konzentration zeichnen sich durch hohe thermische Stabilität aus. Mit steigender Chromoxidkonzentration nimmt der Anteil der irreversiblen gegenüber dem der reversiblen Alterung ab: Eine gute Regenerierbarkeit der Katalysatoren setzt eine Chromoxidreserve voraus.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19744070107
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  • 10
    Electronic Resource
    Electronic Resource
    Beeinflussung der katalytischen Eigenschaften von Al2O3—SiO2-Katalysatoren durch Alkalivergiftung (1974)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 403 (1974), S. 72-80 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Effect of Alkali Contamination on the Catalytic Properties of Al2O3—Si2Catalytic properties of amorphous Al2O3—SiO2 catalysts containing different amounts of Al2O3 in dehydration of isopropanol and cracking of cumene were examined after a defined contamination of the acid centers by sodium ethylate from alcoholic solution. In both reactions, the catalytic activity is decreased by treatment with sodium ethylate, the cracking of cumene being suppressed at a lower alkali concentration than the dehydration of isopropanol. In dehydration of isopropanol, the dependence of the catalytic activity on the alkali content is influenced strongly by the Al2O3 content of the catalysts. In the cracking of cumene, strongly acid Brönsted centers are active, whereas the dehydration of isopropanol proceeds by joint action of acid Lewis or Brönsted centers, respectively, with basic centers at the surface of the catalyst (hydroxide groups or oxygen anions).
    Notes: An amorphen Al2O3—SiO2-Katalysatoren unterschiedlichen Al2O3-Gehaltes wurden nach definierter Vergiftung der sauren Zentren mit Natriumäthylat aus alkoholischer Lösung die katalytischen Eigenschaften bei der Isopropanoldehydratisierung und bei der Cumolspaltung untersucht. Die Natriumbehandlung vermindert für beide Reaktionen die katalytische Aktivität, wobei die Cumolspaltung bereits bei niedrigeren Alkalikonzentrationen unterdrückt wird als die Isopropanoldehydratisierung. Der Charakter der Abhängigkeit der katalytischen Aktivität bei der Isopropanoldehydratisierung vom Alkaligehalt wird stark vom Al2O3-Gehalt der Katalysatoren beeinflußt. Für die Cumolspaltung sind stark saure BRÖNSTED-Zentren aktiv, während die Isopropanoldehydratisierung unter gemeinsamer Beteiligung von sauren Lewis- bzw. BrÖnsted-Zentren mit basischen Zentren der Katalysatoroberfläche (Hydroxidgruppen oder Sauerstoffionen) abläuft.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19744030109
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